[BUG] Authorization failed - Redirect URI missing slash (http:/localhost and https:/platform.claude.com) - Mac Mini macOS

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Bug Description:
OAuth login completely broken. Server rejecting redirect URIs with missing slash.

Errors seen:

• Authorization failed: Redirect URI http:/localhost:49225/callback is not supported by client
• Authorization failed: Redirect URI https:/platform.claude.com/oauth/code/callback is not supported by client

Environment:

• OS: macOS, Mac Mini
• Claude Code: v2.1.20 and v2.1.76 both tested
• IDE: JetBrains
• Support Ticket: 215473502600074

Impact:
1 year paid subscription, completely unable to login since day one.

What Should Happen?

Terminal receives OAuth callback and logs in successfully

Error Messages/Logs

Authorization failed - Redirect URI http:/localhost:49225/callback is not supported by client
Authorization failed - Redirect URI https:/platform.claude.com/oauth/code/callback is not supported by client

Terminal stays stuck at login screen. Never receives callback.

Steps to Reproduce

1. Install Claude Code on Mac Mini (macOS)
2. Run: claude auth login
3. Browser opens to claude.ai OAuth page
4. Log in and click Authorize
5. Browser redirects but shows error

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

Unknown - never worked for me

Claude Code Version

2.1.20 and 2.1.76 both tested

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_